For PvP to take off, they'll also need some form of a ranking system. That alone will be a lot of motivation for LSes.
They'll also need to nerf damage or increase player hitpoints to make fights last longer for duels. I don't think it'll be very interesting if people die in 2 hits or something.

Oh, don't underestimate how many people want PvP from Japan either. There are posts asking for this on their forums.